They are different for sure, but that doesn't make them bad. I enjoyed Fallout 3 and I loved New Vegas. Are they the same kind of game as 1 and 2? No, not at all, but they are enjoyable all the same. Not everything needs to be the same all the time, you can have different things in the same universe and it can be fun.
By the same "things can never change" logic, Fallout 1 and 2 were no good because they were different from Wasteland, which was their predecessor (the universe was made because Interplay couldn't get the rights to Wasteland from EA).
Evaluate a game on its own merits. Don't demand that it be just like its predecessors.